Structure, dielectric, electrostrictive and electrocaloric properties of environmentally friendly Bi-substituted BCZT ferroelectric ceramics

In this study, environmentally friendly Bi-substituted [(Ba_0.85Ca_0.15)_1-3x/2Bi_x](Zr_0.1Ti_0.9)O₃ (BCZT-xBi) ferroelectric ceramics with x = 0–0.08 were prepared using a solid-state sintering method. The structures, dielectric, electrostrictive and electrocaloric properties of the Bi-substituted BCZT ceramics were thoroughly investigated. With an increase in the Bi³⁺ content, the temperature corresponding to the maximum permittivity (T_m) decreased monotonously. Meanwhile, the broadening of the dielectric peaks and the increase in the relaxation coefficient of the ceramics transformed their typical ferroelectric-to-paraelectric phase transition to diffuse phase transition (DPT). This was further confirmed by the trends shown by the ferroelectric properties of the ceramics. The current peak intensity in current-electric field (I-E) curves decreased with an increase in x and finally became constant, indicating that domain reversal disappeared gradually. High electrostrictive coefficient Q₃₃ values of 0.0307, 0.0299 and 0.0223 m⁴/C² were obtained for the ceramics with x = 0.02, 0.04 and 0.06 respectively. The Q₃₃ values of the ceramics indicated their temperature-insensitive nature over the temperature range of 30–120 °C. Although the maximum value of the electrocaloric adiabatic temperature change (ΔT) (0.91 K) was achieved at x = 0.02, the thermally stability of ΔT is improved with an increase in x from 0.02 to 0.06. The results indicated that x = 0.06 improved the thermal stability of the electrostrictive and electrocaloric performance. By increasing the driving field strength, better electrostrictive and electrocaloric responses could be achieved.